Why does my R9 390 keep crashing at random while playing games?

Black screen crash with buzzing sound from speaker (R9 390)

Getting black screen while playing games with a strange looping buzzing sound (from the speaker - no beep code). Signal gone, no error code. Have to hard reset to be able to do anything. Getting these crashes varies from playing 10 minutes to 1,5 hours of gameplay.

Additional Observations:Can't think of anything what could produce the crash, I had this system for more than 2 years now with no problem. It all started few weeks age with a few crashes -like 1 per week. But now, it's getting really frustrating, I can't really play at all for longer period of time.Things I've tried: